[PATCH v4] PCI: vmd: Add the module param to adjust MSI mode

[korantwork]

From: Xinghui Li <korantli@xxxxxxxxxxx>

In the legacy, the vmd MSI mode can only be adjusted by configuring
vmd_ids table. This patch adds another way to adjust MSI mode by
adjusting module param, which allows users easier to adjust the vmd
according to the I/O scenario without rebuilding driver. There are two
params that could be recognized: on, off. The default param is NULL,
the goal is not to effect the existing settings of the device.

Signed-off-by: Xinghui Li <korantli@xxxxxxxxxxx>
Reviewed-by: Nirmal Patel <nirmal.patel@xxxxxxxxxxxxxxx>
---
 drivers/pci/controller/vmd.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 990630ec57c6..fb61181baa9e 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -34,6 +34,19 @@
 #define MB2_SHADOW_OFFSET	0x2000
 #define MB2_SHADOW_SIZE		16
 
+/*
+ * The VMD msi_remap module parameter provides the alternative way
+ * to adjust MSI mode when loading vmd.ko other than vmd_ids table.
+ * There are two params could be recognized:
+ *
+ * off: disable MSI remapping
+ * on:  enable MSI remapping
+ *
+ */
+static char *msi_remap;
+module_param(msi_remap, charp, 0444);
+MODULE_PARM_DESC(msi_remap, "Whether to enable MSI remapping function");
+
 enum vmd_features {
 	/*
 	 * Device may contain registers which hint the physical location of the
@@ -875,6 +888,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 			return ret;
 
 		vmd_set_msi_remapping(vmd, true);
+		dev_info(&vmd->dev->dev, "init vmd with remapping MSI\n");
 
 		ret = vmd_create_irq_domain(vmd);
 		if (ret)
@@ -887,6 +901,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 		irq_domain_update_bus_token(vmd->irq_domain, DOMAIN_BUS_VMD_MSI);
 	} else {
 		vmd_set_msi_remapping(vmd, false);
+		dev_info(&vmd->dev->dev, "init vmd with bypass MSI\n");
 	}
 
 	pci_add_resource(&resources, &vmd->resources[0]);
@@ -955,6 +970,16 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 	return 0;
 }
 
+static void vmd_config_msi_remap_param(unsigned long *features)
+{
+	if (msi_remap) {
+		if (strcmp(msi_remap, "on") == 0)
+			*features &= ~(VMD_FEAT_CAN_BYPASS_MSI_REMAP);
+		else if (strcmp(msi_remap, "off") == 0)
+			*features |= VMD_FEAT_CAN_BYPASS_MSI_REMAP;
+	}
+}
+
 static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
 	unsigned long features = (unsigned long) id->driver_data;
@@ -984,6 +1009,8 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	if (err < 0)
 		goto out_release_instance;
 
+	vmd_config_msi_remap_param(&features);
+
 	vmd->cfgbar = pcim_iomap(dev, VMD_CFGBAR, 0);
 	if (!vmd->cfgbar) {
 		err = -ENOMEM;
-- 
2.31.1